1. Field of Invention
The present invention relates to a thin film magnetic head and a method of manufacturing the same, and more particularly to a composite type thin film magnetic head constructed by stacking an inducting type writing magnetic transducing element and a magnetoresistive type reading magnetic transducing element, particularly a technique for improving a performance of a thin film writing magnetic head.
2. Description of Related Art
Recently a surface recording density of a hard disc device has been improved, and it has been required to develop a thin film magnetic head having an improved performance accordingly.
The composite type thin film magnetic head has a structure for stacking a recording head intended for the writing and a reproducing head intended for the reading out, and a magnetoresistive element has been widely used in order to improve the performance of the reproducing head.
In general, as such a magnetoresistive element, the element utilizing anisotropic magnetoresistive (AMR) effect has been used so far, but there has been further developed a GMR reproducing element utilizing a giant magnetoresistive (GMR) effect having a resistance change ratio higher than the normal anisotropic magnetoresistive effect by several times. In the present specification, elements exhibiting a magnetoresistive effect such as these AMR and GMR reproducing elements are termed as a magnetoresistive reproducing element or MR reproducing element.
By using the AMR reproducing element, a very high surface recording density of several gigabits per a unit square inch has been realized, and a surface recording density can be further increased by using the GMR element. By increasing a surface recording density in this manner, it is possible to realize a hard disc device which has a very large storage capacity of more than 10 gigabytes and is still small in size. A height (MR Height: MRH) of a magnetoresistive reproducing element is one of factors which determine a performance of a reproducing head including a magnetoresistive reproducing element. The MR height MRH is a distance measured from an air bearing surface on which one end face of the magnetoresistive reproducing element is exposed to the other edge of the element remote from the air bearing surface. During a manufacturing process of the magnetic head, a desired MR height MRH can be obtained by controlling an amount of polishing the air bearing surface.
At the same time, a performance of a recording head is also required to be improved, in accordance with improvement of performance of the reproducing head. In order to increase a surface recording density, it is necessary to make a track density on a magnetic record medium as high as possible. For this purpose, a width of a write gap at the air bearing surface has to be reduced to a value within a range from several micron meters to several sub-micron meters. In order to satisfy such a requirement, the semiconductor manufacturing process has been adopted for manufacturing the thin film magnetic head.
One of factors determining a performance of an inductive type thin film writing magnetic head is a throat height TH. This throat height TH is a distance of a pole portion measured from the air bearing surface to an edge of an insulating layer which serves to separate a thin film coil from the air bearing surface. It has been required to shorten this distance as small as possible. The reduction of this throat height is also decided by the amount of grinding from the air bearing surface. Therefore, in order to improve the performance of the thin film magnetic recording head, it is important that the recording head and the reproducing head are formed with best balance.
FIGS. 1a, 1b–9a, and 9b are cross-sectional views vertical to the air bearing surface showing the successive manufacturing steps of a conventional standard thin film magnetic head, and a cross-sectional view in which the magnetic pole section is cut in parallel to the air bearing surface. Moreover, FIGS. 10–12 are a cross-sectional view of the entire conventional completed thin film magnetic head a cross-sectional view of the magnetic pole section, and a plan view of the entire thin film magnetic head, respectively. Moreover, the thin film magnetic head of this embodiment is a composite type thin film magnetic head formed by stacking the induction type thin film writing magnetic head and the MR reproduction reading element.
First of all, as shown in FIGS. 1a and 1b, an Insulation layer 2 consisting of for example alumina (Al2O3) is deposited on a basic substrate 1 consisting of non-magnetic and electrical insulation material for example, such as AlTiC with a thickness of about 5–10 μm.
Next, as shown in FIGS. 2a and 2b, a lower shield layer 3, which composes a magnetic shield protecting the MR reproduction element of the reproducing head from the influence of the external magnetic field, is formed with the thickness of 3 μm.
Afterwards, as shown in FIGS. 3a and 3b, after spattering and depositing alumina by the thickness of 100–150 nm, a magnetic resistance layer 5 consisting of a material with the effect of magnetic resistance and composing the MR reproduction element is formed on a shield gap layer with the thickness of tens nano meter, thereby making high precise mask alignment.
Then, as shown in the FIG. 4, again, a shield gap layer 6 is formed so that the magnetic resistance layer 5 is embedded in the shield gap layers 4 and 6.
Next, as shown in the FIG. 5, a magnetic layer 7 consisting of permalloy is formed with the film thickness of 3 μm. This magnetic layer 7 has not only a function of the upper shield layer which magnetically shields the MR reproduction element together with the above described lower shield layer 3, but also has a function of a lower magnetic layer of the thin film magnetic writing head. Herein, for convenience sake of the explanation, this magnetic layer 7 is called as a first magnetic layer by paying attention to it a magnetic layer composing a writing magnetic head.
Then, on the first magnetic layer 7, after a light gap layer 8 consisting of non-magnetic material, for example alumina is formed with film thickness of about 200 nm, a second magnetic layer 9 consisting of material with high saturation magnetic flux density such as, for example, permalloy (Ni: 50 wt %, Fe: 50 wt %) and nitride iron (FeN) is formed with a desired shape by high precise mask alignment.
Second magnetic layer 9 molded in a given shape is called a pole chip, and the width of the track is defined as a width W.
In this case, when a dummy pattern 9′ for connecting a lower pole (first magnetic layer) and an upper pole (third magnetic layer), which is formed latter, are formed simultaneously, it is possible to make an opening for through-hole after a polishing or chemistry-mechanical polishing (CMP).
In order to prevent a width of effective writing track from being widened. That is, in order to prevent a magnetic flux from being widened in the lower pole at the data writing, also a gap layer 8 in surroundings of the pole chip 9 and the lower pole 7 (first magnetic layer) are etched by an ion beam etching, such as, ion miring. Even though its state is shown in FIG. 5b, this structure is called as a trim, and this portion becomes a magnetic pole section in the first magnetic layer.
Next, as shown in FIGS. 6a and 6b, after an insulating layer, for example, alumina film 10 is formed with the thickness of about 3 μm, the whole is, for example, made smooth by CMP.
Subsequently, after forming a photoresist layer 11 of electrical insulation to a given pattern by the mask alignment of high precision, a thin film coil 12 as the first layer consisting, for example, of copper is formed on the photoresist layer 11.
Continuously, as shown in FIGS. 7a and 7b, after forming an insulating photoresist layer 13 is formed on the thin film coil 12 by the mask alignment of high accuracy again, in order to make the surface smooth, the calcining (baking) processing is given with the temperature of for example 250–300° C.
In addition, as shown in FIGS. 8a and 8b, the thin film coils 14 as the second layer are formed on the smoothed surface of this photoresist layer 13. Next, after forming a photoresist layer 15 with highly accurate mask alignment on the thin film coils 14 as this second layer, in order to make the surface smooth again, the calcining (baking) processing is given with the temperature of for example 250° C.
As described above, the reason why photoresist layers 11, 13 and 15 are formed with mask alignment of high accuracy, is that throat height and MR height are defined by a reference position at the end edge of the magnetic pole section side of the photoresist layer.
Next, as shown in FIGS. 9a and 9b, a third magnetic layer 16 consisting of for example permalloy is selectively formed on the second magnetic layer 9 (pole chip) and the photoresist layers 11, 13 and 15 with the thickness of 3 tm according to desired pattern.
This third magnetic layer 16 comes in contact with the first magnetic layer 7 at a rear position away from the magnetic pole section through a dummy pattern 9′, thin film coil 12, 14 is extended through a closed magnetic circuit composed by the 1st, 2nd and 3rd magnetic layers.
In addition, an overcoat layer 17 consisting of alumina deposited from the exposed surface of the third magnetic layer 16.
Finally, the side surface forming the magnetic resistance layer 5 and the gap layer 8 is ground, thereby forming an air bearing surface (ABS) 18 opposite to the magnetic record medium. Magnetic resistance layer 5 is also ground in the formation process of this air bearing surface 18, and thus, MR reproduction element 19 is obtained. In this way, the above described throat height TH and the MR height MRH are decided. Its appearance is shown in FIG. 10. In an actual thin film magnetic head, the conductor and the point of contact pad for performing electrical connection for the thin film coils 12, 14 and a MR reproduction element 19 are formed, but this is not shown.
As shown in FIG. 10, an angle θ between line segments S connecting corners of side surfaces of photoresist layers 11, 13, 15 for isolating the thin film coils 12, 14 and an upper surface of the third magnetic layers 16 is called as an apex angle thereby becoming an important factor for deciding a performance of the thin film magnetic head together with the above described throat height TH and MR height.
Moreover, as shown in FIG. 12 by the plane, a width W of the magnetic pole section 20 between the second magnetic layer 9 and the 3rd magnetic layer 16 is made narrow, and the width of the track recorded in the magnetic record medium is defined by this width, so that it is necessary to narrow this width W as much as possible to achieve a high surface recording density. Moreover, in this FIG. 12, for the shake's of convenience of drawing, the thin film coils 12, 14 are made concentric circle.
Well, in forming conventional thin film magnetic head, especially, the problem is that after forming the coil, the coil section covered with the photoresist insulation layer and risen in the mountain shape, especially, it is a difficulty of a fine formation of the upper pole (yoke pole) formed along the inclined part (Apex). That is, the hitherto, in case of forming the upper pole, after plating the material for the upper pole such as permalloy on the mountain shaped coil with the height of about 7–10 μm, the photoresist is spread with the thickness of 3–4 μm, after which a given pattern is formed by using the photolithography technology. Herein, If 3 μm or more is necessary as the film thickness of resist that the patterning is performed by the register strike on the mountain shaped coil, the photoresist of the about 8–10 μm thickness will be spread under the inclined portion.
On the one hand, in the upper pole formed on the write gap layer which is formed on the surface and the smooth surface of a certain mountain shaped coil section having the height difference of about such 10 μm, it is necessary to form the narrow track of the recording head near the edge in the photoresist insulation layer (11, 13 of for example FIG. 7). Therefore, it is necessary to form the pattern of the width of 1 μm with the photoresist film of thickness of 8–10 μm.
However, even if the narrow width pattern of 1 μm level is formed with a photoresist film as thick as 8–10 μm, in case of exposing the photolithography, the pattern crumble or the like due to the reflection of light is generated, and the decrease in the resolution is forced due to the thick resist, so that it is extremely difficult to form a top pole for forming the narrow track by the patterning with accuracy.
Then, as is shown in the above conventional embodiment, assuming that data is written with the pole chip capable of forming the narrow track width of the recording head, after forming this pole chip, by adopting a method of connecting the upper pole to this pole chip, in other words, by adopting a structure divided into two, that is, a pole chip for determining the track width and an upper pole for inducing magnetic flux, the above problem has been advantageously improved.
However, in the thin film magnetic head formed as in the above, particularly, in the recording head, the problem described as follows was left now as in the past.
(1) The contact area of a pole chip and an upper pole is small, moreover, the contact portion touches it vertically, so that it is easy to saturate magnetic flux with the part, therefore, the writing characteristic of satisfying enough is not obtained.
(2) Throat height TH and MR height MRH are decided based on the edge on the pole portion side of the insulating layer which insulating separates the thin film coil, but the insulating layer is weak to heat since it is usually formed with a photoresist organic insulating layer.
Therefore, it melts by heat-treating about 250° C. added when the thin film coil is formed or softens, and the pattern size of the insulating layer changes, and the size of throat height TH and MR height MRH might shift from the design value of the desire.
(3) The positional relation of a pole chip and an upper pole is decided by alignment at photolithography, so that seen from the air bearing surface, this positional relation is shifted to one side greatly, but in this case, data writing is performed even in the upper pole and thus the effective track width is widened. Therefore, the malfunction of writing the data in the place other than in the hard disk board to be recorded originally, is generated.